Carburetor device



Jan. 23, 1940. H. w.- FARR CARBURETOR DEVICE Filed Aug. 10, 1938 E n m MW 7 .1? j Q Ifluen/Br Henry W- Farr By M Z Patented Jan. 23, 1940 UNITED STATES OARBUBETOB DEVICE Henry W. Farr, Royal Oak, Mich, assignor to Carter Carburetor Corporation, St. Louis, Mo., a corporation Delaware 6 Claims.

This invention relates to automatic choke devices for internal combustion engine carburetors, particularly of the type utilizing a suction piston for opening the choke valve when the engine fires 8 and starts to run after cranking.

Cofiey Patent No. 2,085,351 illustrates a well known form of automatic choke control in which a thermostat and a suction piston are mounted in a housing carried adjacent the carburetor air horn. The cylinder receiving the suction piston has a by-pass recess so that a part of the suction is utilized, for drawing heated air from a stove suitably mounted on the engine manifold, through the housing and into the carburetor barrel posterior to the throttle. This arrangement is satisfactory where the pressure in the engine intake remains constantly below atmospheric pressure, but where a supercharger is provided, the pressure in the engine intake, at times, exceeds atmospheric pressure with the result that the suction piston is urged outwardly in a direction to close the choke. This, in turn, results in undesirable enrichening of the mixture since modern automotive carburetors are of the plain tube type and constructed to provide the proper mixture under all normal operating conditions without variation of the choke valve from its full open position.

An object of the present invention is to provide so an automatic choke device of the above type including means for avoiding any tendency to close the valve due to the existence of superatmospheric pressure in the engine intake manifold.

Another object is to provide an automatic choke 35 device of the above type with means for applying super-atmospheric pressure in the engine intake manifold to the suction piston in such a manner as to tend to hold the choke valve open instead of urging the valve in the closing direc- 49 tion.

These objects and other more detailed objects hereafter appearing are attained in the accompanying drawing in which the figure is a side view of a carburetor, partly broken away and 5 sectioned for clearer illustration.

The carburetor shown includes a downdraft barrel l, forming a, mixture conduit, and a bowl 2 within which a supply of fuel is maintained at a substantially constant level by means of any 50 suitable mechanism (not shown) such as a float controlled needle valve. Mounted in the upper or air horn portion 3 of the carburetor barrel is an unbalanced butterfly-type choke valve 4, having its supporting shaft extending into an insu- 55 lated housing 5 carried adjacent the air horn.

ApplieatiomAugust .10, 1938, Serial No. 224,018

' Secured rigidly to the end of the more shaft is a crank 6 having an outwardly projecting finger I and a curved arm 8, the latter being connected by means of a link 9 to suction piston l0. Piston l0 reciprocates in a cylinder ll, formed in the wall 5 of housing 5 and communicating through a passage I! with the interior of the carburetor barrel posterior to throttle valve l3.

Also mounted in housing 5 is a coiled, bi-metal thermostat i4 having its inner end rigidly secured 10 to a pintle IS on the housing wall and having its outer end hooked as at l6 for cooperating with finger I on crank 6. The thermostat is of such character as to unwind when the temperature is relatively low, closing the choke valve. 'As the temperature increases, the thermostat winds upon itself, thus releasing the choke valve which opens due to its unbalanced weight and also due to suction applied directly to the valve and to suction piston l0. Flutings H are provided in the wall of 20 cylinder ll so that when suction piston I0 is in an intermediate or fully depressed position, a por tion of the suction from passage I2 is by-passed therearound so as to draw heated air from a stove device l8 mounted on exhaust manifold I9, 26 through heater tube 20, housing 5, and passage l2 into the carburetor barrel. This action tends to heat the thermostat in accordance with the temperature of the engine firing chambers. Stove device I8 is open to atmosphere, as at 2|, so that 30 substantially atmospheric pressure exists in tube 29 and the housing.

In cases where the pressure in the engine intake exceeds atmospheric pressure, such positive pressure transmitted through passage 12 to the bottom of suction piston l0, would tend to raise the piston and close the choke valve. In order to prevent such action, there is provided a by-pass including passages 22 and 23 from passage l2 around. cylinder II. A restriction 24 forms a 40 valve seat in passage l2 between the by-pass and the cylinder and a ball check 25 cooperates with this restriction to close the communication between cylinder II and passage l2 whenever the pressure in passage I2 exceeds that in housing 5. 5 Such super-atmospheric pressures are transmitted through by-pass 2223, past ball check 26, directly to housing 5 and to the top portion of piston Ill so as to urge this piston downwardly towards its normal running position. An addi- 5o tional ball check 21 is provided in heater passage 20 to prevent the blowing out of such positive pressures through the stove.

During periods when the engine intake pressure exceeds atmospheric, due to the supercharger action, the pressure in casing or housing 5 will be correspondingly increased, check 21 preventing the passage of a constant draft from the carburetor through the stove which might tend to cool the thermostat. Thus, by means of the arrangement shown, the automatic choke control will function in its intended manner with a supercharged engine.

Various details of the structure shown are not essential and these may be modified as will occur to those skilled in the art, without departing from the spirit of the invention. The exclusive use of all such modifications as come withinthe scope of the appended claims is contemplated.

I claim:

1. A carburetor choke control including a housing having a connection with a source of heated fluid, a suction passage connecting said housing with a zone of varying pressures, a thermostat in said housing, a pressure responsive device in said passage, and a check valve in said suction connection between said device and said zone arranged to open only when the pressure in said passage is less than that in said housing.

2. The combination as specified in claim 1 further including a bypass extending from said passage to said housing around said pressure responsive device and said check valve for connecting said housing with said passage when the pressure in said passage is greater than that in said housing.

3. The combination as specified in claim 1 further including a by-pass for connecting said passage and said housing when said check valve is closed, and a second check valve in said by-pass arranged to open only when the pressure in said passage exceeds that in said housing.

4. The combination as specified in claim 1 further including a by-pass for connecting said passage and said housing when said check valve is closed, and a second check valve in said by-pass to prevent passage therethrough oi fluid from said heater connection and said housing.

5. The combination as specified in claim 1 further including by-pass means for connecting said passage and said housing when said check valve is closed, a second check valve in said by-pass means to prevent passage therethrough of fluid from said heater connection and said housing, and a check valve in said heater connection to prevent passage therethrough 01' fluid from said housing and said suction connection.

6. The combination with an internal combustion engine having an intake conduit, a choke valve therein, and a choke control comprising a housing having a heater connection and a suction passage connecting said housing with said intake, a choke controlling thermostat in said housing, a suction piston in said passage for opening the choke when substantial suction exists in said intake, 9. by-pass extending from said passage to said housing around said piston for drawing heated fluid from said heater connection through said housing, a check valve in said suction passage between said piston and by-pass and said intake conduit arranged to close when p the pressure in said conduit exceeds that in said housing, a second by-pass extending from said suction passage to said housing around said piston and said check valve for connecting said housing andsaid passage when said check valve is closed, and a check valve in said second by-pass to prevent the passage of fluid therethrough from said heater connection and said housing into said passage.

HENRY W. FARR. 

